Heart disease is the leading cause of death for both women and men in the United States. One of the most common forms of heart disease is coronary artery disease (CAD). In 2006 alone, CAD killed 425,245 people, and 176,138 coronary artery bypass grafts were implanted in patients [1]. The need for an alternative vascular substitute is warranted as autologous vessels (e.g., mammary artery, saphenous vein) are oftentimes unavailable due to prior use or cardiovascular disease. Providing a functional tissue engineered vascular graft (TEVG) for CABG surgeries would therefore result in drastic improvements in patient care. Despite significant progress by several research groups in the last few decades, a mechanically and biologically functional TEVG has yet to be developed [22-26]. The overall working hypothesis of this proposal is that a TEVG composed of alternating layers of SMC embedded collagen/fibrin and cross-linked human tropoelastin will result in a vascular substitute that can be compliance-matched to that of a native porcine coronary artery. The primary goal of this research proposal is to fabricate a TEVG that is composed of non-synthetic polymers arranged in a fashion that mimics native vessel architecture and that is compliance matched to a native porcine coronary artery. This goal will be met by completing the following specific aims. Specific Aim 1a: Determine, as a function of time in culture, the biomechanical properties and load dependent extracellular matrix (ECM) microstructural organization of the individual layers to be used in the final optimized TEVG. Specific Aim 1b: Quantify how the addition of exogenous TGF2 affects the biomechanical properties and load dependent ECM microstructural organization of the pASMC embedded collagen/fibrin constructs. Specific Aim 2a: Use a computational optimization procedure to identify the optimum number and thickness of alternating tropoelastin and pASMC embedded layers that result in a TEVG whose compliance matches that of porcine coronary artery. Finally, our last aim (Specific Aim 2b) will be to determine if TEVGs fabricated using the optimized parameters (from SA2a) are compliance matched and have similar microstructure to a porcine coronary artery. Successful completion of the proposed aims will result in a TEVG that is constructed entirely from non- synthetic materials, is inspired by native arterial microstructure, and displays the compliance of a functional coronary artery. Our proposed research will also generate novel experimental information on how the compliance and extracellular matrix organization of developing constructs are coupled as they develop in culture. !